Conventionally, there has been disclosed a device that adjusts a NOx value of exhaust gas by controlling humidity of intake air of an internal combustion engine based on absolute humidity, for example, in Patent Literature 1. In this device, absolute humidity is calculated from relative humidity that is detected by a humidity sensor and a temperature of intake air that is detected by a temperature sensor. Subsequently, the opening degree of a humidity adjustment damper provided at an intake duct that feeds highly humid air is adjusted so that the calculated absolute humidity becomes a target value.
Following is a list of patent literatures which the applicant has noticed as background arts of embodiments the present disclosure.
Patent Literature 1: JP 2002-048010 A
Patent Literature 2: JP 2003-148135 A